Method and system for de-oiling a feed of oil and water

ABSTRACT

A method and system for de-oiling a feed comprising oil and water. The feed has an input temperature above the boiling point of water and an input pressure sufficient to maintain the water in a liquid state. In at least one embodiment, the method comprises pumping the feed with a motive pump through a phase separator having a restriction to effect a phase separation of oil and water in the feed and produce an agitated mixture, supplying the agitated mixture from the phase separator into a pressure vessel operating at a pressure sufficient to maintain in a liquid state water that is at a temperature above the boiling point of water, removing an oil phase from the pressure vessel, and removing a water phase from the pressure vessel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 USC 119(e) of U.S.provisional application Ser. No. 61/862,886 filed Aug. 6, 2013.

BACKGROUND

Many fluid systems in the oil industry store or produce a fluidcontaining oil and water at temperatures over one hundred degreesCelsius and under pressure to prevent boiling. Before de-oiling, suchfeeds are cooled with a heat exchanger and cooling circuit prior totreatment in one or more flotation cells.

SUMMARY

A method is disclosed of de-oiling a feed comprising oil and water, thefeed having an input temperature above the boiling point of water and aninput pressure sufficient to maintain the water in a liquid state, themethod comprising: pumping the feed with a motive pump through a phaseseparator having a restriction to effect a phase separation of oil andwater in the feed and produce an agitated mixture; supplying theagitated mixture from the phase separator into a pressure vesseloperating at a pressure sufficient to maintain in a liquid state waterthat is at a temperature above the boiling point of water; removing anoil phase from the pressure vessel; and removing a water phase from thepressure vessel. A system for carrying out the method.

A system is also disclosed for de-oiling a feed comprising oil andwater, the system comprising: an input point connected to receive thefeed, the feed having an input temperature above the boiling point ofwater and an input pressure sufficient to maintain the water in a liquidstate; a motive pump connected to pump the feed from the input pointthrough a phase separator having a restriction to effect a phaseseparation of oil and water in the feed and produce an agitated mixture;a pressure vessel connected to receive the agitated mixture, thepressure vessel having a pressure sufficient to maintain water, which isabove the boiling point of water, from the agitated mixture in a liquidstate; an oil phase outlet connected to the pressure vessel; and a waterphase outlet connected to the pressure vessel.

In various embodiments, there may be included any one or more of thefollowing features: The pressure vessel, motive pump, and phaseseparator are housed on a mobile platform having an input pointconnected to the motive pump, and further comprising the initial stagesof: transporting the mobile platform to a work site containing the feed;and connecting the feed to the input point. The mobile platform is freeof fluid cooling devices between the input point and the pressurevessel. The mobile platform comprises a skid or trailer. The feedcomprises slop oil. Supplying the water phase to an amine plant fortreatment of sour gas. Supplying a gas blanket at or above 500 kPa tothe pressure vessel. Pumping the water phase through a second phaseseparator having a restriction to effect a phase separation of oil andwater in the feed and produce a second agitated mixture; supplying thesecond agitated mixture from the phase separator into a second pressurevessel operating at a pressure sufficient to maintain in a liquid statewater that is at a temperature above the boiling point of water;removing an oil phase from the second pressure vessel; and removing awater phase from the second pressure vessel. The phase separatorcomprises a mixing chamber downstream of the restriction, and the feedis pumped through the restriction and mixed with a gas in the mixingchamber. Removing from the pressure vessel a sample through a sampleline, the sample line being connected to a cooling device. The sampleline is connected to a fume hood. The cooling device is a heat exchangerconnected to a refrigeration loop. The pressure vessel is a flotationcell. The system is housed on a mobile platform. A gas blanket pressuresource is connected to the pressure vessel. A housing contains themotive pump, the pressure vessel, the oil phase outlet and the waterphase outlet.

These and other aspects of the device and method are set out in theclaims, which are incorporated here by reference.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments will now be described with reference to the figures, inwhich like reference characters denote like elements, by way of example,and in which:

FIGS. 1-3 collectively illustrate a schematic of a system and method forde-oiling a feed of oil and water.

FIG. 1A is a view illustrating the linkage between the partial viewsshown in FIGS. 1-3.

FIG. 4 is a schematic of a system of de-oiling slop oil for use in anamine plant.

FIG. 5 is a side elevation section view of a phase separator.

DETAILED DESCRIPTION

Immaterial modifications may be made to the embodiments described herewithout departing from what is covered by the claims.

At many oil field sites, for example at a well site, refinery, or otherinstallation, there are sources of high pressure, high temperature, oilywater. Examples include slop oil or fluids produced from a well.Treatment of high temperature high pressure oily water involves thefollowing process. The fluid leaves a pressurized storage vessel orline, and passes through one or more coolers such as a heat exchangerscarrying coolant to cool the fluid below the boiling point of water.Cooled fluid is then discharged into a fluid treatment system thatoperates at or slightly above atmospheric pressure, such system usuallyincorporating one or more cascading flotation cells, such as induced gasflotation cells.

Often times the water output from de-oiling systems is used in processesthat require a hot water input at over one hundred degrees Celsius. Insuch cases, a heater such as a second heat exchanger must be used toraise the temperature of the output water.

The use of input and output heat exchangers with de-oiling systemscreates a bottleneck in the industry that consumes energy and requiresadditional infrastructure to operate above and beyond the de-oilingequipment. In addition, such heat exchangers are often easily fouledfrom the passage of oily water feeds.

Referring to FIGS. 1-3, a method and system 10 of de-oiling a feed 12 isillustrated. Feed 12 comprises oil and water. Feed 12 also has an inputtemperature above the boiling point of water and an input pressuresufficient to maintain the water in a liquid state.

Feed 12 is pumped with booster or motive pump P-100 through a phaseseparator RJOSPS-100. The phase separator RJOSPS-100 has a restriction14 (discussed further below with reference to FIG. 5), and effects aphase separation of oil and water in the feed to produce an agitatedmixture outputted into line 16. The agitated mixture is then suppliedfrom the phase separator RJOSPS-100 through line 16 into a pressurevessel V-100, which may be a flotation cell, operating at a pressuresufficient to maintain in a liquid state water that is at a temperatureabove the boiling point of water. For example, V-100 may be at or above500 kPa, of which pressure may be supplied by a gas blanket from line 18(gas blanket pressure source). Line 18 may connect to one or more gastanks. The gas used in the gas blanket may include natural gas or inertgas such as nitrogen and may be provided over the components of thevessel V-100 during use. Other gases or mixtures of gas may be used. Agas blanket may be set up using piping to all tanks and lines of system10 as shown to exclude oxygen and maintain a non-explosive atmosphere.

Line 16 may discharge through an inlet 20 such as a diffuser (not shown)at a fluid surface such as an oil fluid surface or a fluid interfacebetween water and oil in the vessel V-100. Such location of inlet 20permits gentle dispersion of the agitated mixture into the pressurevessel V-100 without vigorous contact with the fluid already in thevessel V-100.

An oil phase is removed via line 22 (oil phase outlet) from the pressurevessel V-100, for example, using an oil removal device such as a weir24. Vessel V-100 operates as a separator tank where oil is separatedfrom water by floating on top of the water. A water phase is removed vialine 26 (water phase outlet) from vessel V-100, from an outlet position30 lower than the outlet position 28 of line 22.

Fluids from feed 12 may be treated in one or more cascading pressurevessels, for example, vessels V-100, V-101, and V-102. Thus, forexample, the water phase from vessel V-100 may be pumped with pump P-101through a second phase separator RJOSPS-101 and supplied as an agitatedmixture view line 16-1 into a second pressure vessel V-101 operating ata pressure sufficient to maintain in a liquid state water that is at atemperature above the boiling point of water. The components of eachsubsequent stage of fluid separation may function in a similar fashionas the components of the preceding stage. Thus, for example, vesselV-101 operates like vessel V-100 with an oil phase being removed vialine 22-1 and a water phase being removed via line 26-1. Similarly, pumpP-101 and phase separator RJOSPS-101 may operate in the same fashion aspump P-100 and RJOSPS-100, respectively. The water phase removed vialine 26-1 may be further processed, with phase separator RJOSPS-102 andvessel V-102, both of which operate like preceding pump P-100 and phaseseparator RJOSPS-100, respectively.

Oil removed from one or more of pressure vessels V-100, V-101, and V-102may be further processed, for example, by combining into a single line23 that feeds an oil emulsion tank V-103, which may also be a pressurevessel operating under pressure. Oil emulsion tank V-103 may have awater drain (not shown), and may output processed oil through one ormore transfer pumps P-105 (such as a lobe pump) on a line 32 to anoutlet 34 of system 10. A heat exchanger such as a spiral exchangerE-110 may be used to cool the oil in line 32 if desired.

In general, all the pressure vessels described in this document mayoperate at a pressure sufficient to maintain in a liquid state waterthat is at a temperature above the boiling point of water. By keepingthe pressure vessels at such pressures, the flashing of hot water intosteam from processed fluids is reduced or eliminated, and there is noneed to reduce the temperature of feed 12 fluids prior to processing.

One or more components of system 10 may be housed on a mobile platform40, such as at least the pressure vessel V-100, motive pump P-100, andphase separator RJOSPS-100. In a further example, all the componentsillustrated in FIGS. 1-3 are housed on platform 40, which may be a skidor trailer for example. In some cases, the dashed lines 40 may delineatea protective housing located on platform 40. Platform 40 has an inputpoint 13 connected to the motive pump P-100. Referring to FIG. 4, theplatform 40 may be transported, for example by trailer or rail, to awork site 42 containing the feed 12, for example in the form of anoutlet from a feed source such as a slop oil tank 44. Once present atwork site 42, feed 12 is connected to the input point 13 of system 10.Referring to FIGS. 1-3, the mobile platform 40 may be free of fluidcooling devices at least between the input point 13 the pressure vesselV-100. In some cases, no fluid cooling devices may be present betweeninput point 13 and de-oiled water output 48 or oil emulsion output 34,though the examples shown incorporate optional output heat exchangersE-100 and E-110 if the client desires a cool output feed. A system 10 ofthe sort illustrated may be brought to a work site 42, plugged in to ahot feed 12, and used to process fluids without consuming additionalresources to cool and heat fluids.

Fluid processing of the sort described in this document may becharacterized as thermodynamically passive, with no additional heatbeing supplied to fluids during processing for the purpose ofmaintaining the water in such fluids above an ambient boilingtemperature of water. A passive system permits the hot water togradually cool as it is processed within system 10, though the resultingoutput stream 48 may likely still be above ambient boiling temperature.Ambient boiling temperature is region and elevation specific and isunderstood to mean the temperature at which water would boil if atambient pressure.

One or more or all of the pressure vessels may connect to a vaportakeoff line 36 for removal of volatile hydrocarbons and otherlow-boiling liquids from the fluids. Line 36 may supply such take-offfluids to be further processed or disposed for example via a flareheader. Pressure safety valves 38 may be present on all vessels V-100,V-101, V-102, and V-103. Pressure safety valves such as valves 50 and 52may be used in other parts of system 10 as desired.

Referring to FIG. 4, as discussed above the feed 12 may comprise slopoil, for example, in a tank 44. Slop oil is the collective term formixtures of oil, chemicals and water derived from a wide variety ofsources in refineries or oil fields. Slop oil may be formed when tankwagons and oil tanks are cleaned and during maintenance work or inunforeseen oil accidents. Slop oil may be at a temperature above theambient boiling temperature of water, but in a pressurized liquid state.

The water phase remove from one or more of vessels V-100, V-101, orV-102 (for example from outlet 48) may be supplied to a downstreamsystem that requires a hot water feed. One such system is an amine plant54 for treatment of sour gas. Amine plants may be positioned at wellsites in order to safely process sour gas after extraction from a well.Prior to use, output water may be treated after system 10, for example,by resin treating to remove for minerals, silica, and dissolved salts.Output water may also be used in other applications such as use as aboiler feed for steam production in a steam assisted gravity drainageoperation. Output water may also be used in refinery gas and oily glycolapplications.

Referring to FIGS. 1-3, samples may be removed from any one or more ofpressure vessels V-100, V-101, V-102, V-103, and other points of thesystem 10 such as lines 12, 34 and 48 as shown. Samples may be analyzedto monitor and adjust system operation. For example, referring to V-100,a sample may be removed through a sample line 68 that makes up part of asample removal system 69. A filter such as a glass filter GF-101 may beused or bypassed via line 70 to remove solids. An air supply line 78 maysupply fume hood FH-10 with supply air, which may pass through aninduced draft fan 80.

The sample line 68 may be connected to a cooling device such as a heatexchanger SC-101 connected to circulate coolant. Cooling the samplesallows the samples to be discharged into an analysis unit like a fumefood FH-100 at ambient pressure. The coolant may be circulated from arefrigeration circulation loop or system 70, which may circulate coolantsuch as glycol. System 70 may have a coolant supply line 72, acompressor or air cooler C-100, a return line 74, a glycol expansiontank TK-100, and a pump P-104 such as a centrifugal pump. Coolant fromsupply line 74 may supply one or more or all heat exchangers in thesystem 10, including output fluid cooling heat exchangers E-100 andE-110, which each may have a bypass 76.

Referring to FIG. 5, each phase separator, for example RJOSPS-100, maycomprise a conduit 56, a mixing chamber 58, and a port 60. Pump P-100(FIG. 1) may be provided as part of the phase separator RJOSPS-100. Arestriction 14 in the conduit 56 may form a nozzle through which feed 12flows when the pump P-100 is operated. The conduit 56 may have a mixingchamber 58 downstream of the restriction 14 and a port 60 for admissionof gas, for example, from line 18 through turbine flow meter unit M-100(FIG. 1) into the mixing chamber 58 for example, in an initial portionof the mixing chamber 58, to cause the feed to foam. By mixing gas withthe feed 12 in a turbulent manner, the feed 12 may be foamed, whichfacilitates removal of the oil phase from the separator V-100. Inductionof gas may produce pico bubbles in the stream that attach to eachdroplet of oil to remove the oil from the water or solid phases.

In the example shown, the mixing chamber 58 may terminate downstream ata transition 66 in the conduit 56 to a larger diameter portion 16 of theconduit 56. The mixing chamber 58 may have a length to internal diameterratio of at least 20:1 or 40:1, preferably in the range 50:1 to 60:1.The mixing chamber 58 may have constant internal diameter along thelength of the mixing chamber 58. When the mixing chamber 58 does nothave constant internal diameter, the internal diameter of the mixingchamber 58, for the purpose of calculating the length to internaldiameter ratio, may be the mean internal diameter. The internal diameterof the mixing chamber 58 may be selected so that the fluid exiting therestriction 14 undergoes turbulence and collision with all parts of theinternal wall of the mixing chamber 58. The mixing chamber 58 may needonly begin after the fluid exiting the restriction 14 has expandedsufficiently to contact the walls of the mixing chamber 58.

Although the phase separator RJOSPS-100 may not pump anything other thanair from the port 60 for mixing with feed 12, RJOSPS-100 may have thegeneral design of a jet pump in terms of the relationship of the size ofthe mixing chamber to the restriction. The port 60 may be locateddownstream of the restriction 14 and before the mixing chamber 58. Theconduit immediately downstream of the restriction 14 should have adiameter sufficient to accommodate the jet exiting the restriction 14.The mixing chamber 58 may have an internal diameter that is less thanthe internal diameter of the conduit 56 (before the restriction 14) andgreater than the diameter of the restriction 14. For a 12 inch internaldiameter mixing chamber 58, the mixing chamber 58 may be 40 feet long.For treatment of tailings, the diameter of the restriction 14 may beselected to provide a pressure in the conduit 56 before the restriction14 of 75 psi to 150 psi. The conduit 16 after the transition 66 may havean internal diameter equal to the internal diameter of the mixingchamber 58.

The port 60 preferably comprises a valve, which may be controlledmanually or automatically such as by controller (not shown). When theport 60 is not open, a vacuum created in the conduit 56 downstream ofthe pump P-100 may cause vibration within the pipe and poor separationof the fluid components. When the port 60 is opened sufficiently for thevibration to stop, the fluid components may be agitated and a phaseseparation may occur within the fluid so that oil may be stripped fromsolids. Gas, for example, air introduced through the port 60 may becomeentrained with the fluid components and tends to adhere to oil in thefluid. Thus, the phase separator agitates the fluid removed from theflotation cell in the presence of a gas to cause the fluid to foam.

The discharge from line 16 may pass into a pressure vessel V-100 that isnot a flotation cell, for example, a centrifuge, hydro-cyclone oranother fluid treatment apparatus. Any number of additional suchsecondary separation apparatus may be used as necessary to effect anadequate phase separation.

The feed 12 having components to be treated may comprise solids such astailings from a tailings pond, such as a tailings pond at a heavy oilmining facility. The operation of one or more of pumps, for example,P-100 and P-101 respectively preceding and following a pressure vesselV-100 may be operated to maintain the working fluid level in thepressure vessel V-100 within a predetermined range independent ofvariations in the oil concentration of the feed.

A slightly wet solid phase may be drained from the base of one or moreof pressure vessels V-100, V-101 and V-102. The wet solids may beallowed to dry or dried in various ways, such as with the addition ofheat, but may also be allowed to drain. Once dried, the solids may bereturned to a reclaimed mine site or subject to further processing, forexample to extract minerals from the solids.

To avoid redundancy in the description and drawings, reference elementsor accompanying description has not been explicitly added for certainrepeated components. For example, line 16-2 is not discussed but isunderstood to function in a fashion similar to 16-1 and 16. As well, thelines and components of all but one of the sample removal systems 69 aredelineated in detail in the description and drawings, yet it isunderstood that the other sample removal systems may function in afashion similar to the description sample removal system 69 (shown inFIG. 1).

Other components not discussed in detail may be incorporated. Forexample, in one case feed 12 is filtered with a basket strainer prior tosupply to pump P-100. Pumps may be suitable pumps such as centrifugalpumps. Coolant from cooling system 70 may be used to cool pump seals onthe motive pumps such as P-100, using for example a shell and tubeexchanger connected to line 72. Various valves, bypasses, and piping maybe incorporated. Heat exchangers include various types of heatexchangers beyond merely the examples given above. One or morecontrollers may be used to operate part or all of system 10.

In the claims, the word “comprising” is used in its inclusive sense anddoes not exclude other elements being present. The indefinite articles“a” and “an” before a claim feature do not exclude more than one of thefeature being present. Each one of the individual features describedhere may be used in one or more embodiments and is not, by virtue onlyof being described here, to be construed as essential to all embodimentsas defined by the claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A system for de-oiling afeed comprising oil and water, the system comprising: an input pointconnected to receive the feed, the feed having an input temperatureabove the boiling point of water and an input pressure sufficient tomaintain the water in a liquid state; a motive pump connected to pumpthe feed from the input point through a phase separator having arestriction and a mixing chamber downstream of the restriction, to mixthe feed with a gas in the mixing chamber to effect a phase separationof oil and water in the feed and produce an agitated mixture; a pressurevessel connected to receive the agitated mixture through a lineconnecting the motive pump to the pressure vessel through the phaseseparator, the pressure vessel having a pressure sufficient to maintainwater, which is above the boiling point of water, from the agitatedmixture in a liquid state; an oil phase outlet connected to the pressurevessel; and a water phase outlet connected to the pressure vessel. 2.The system of claim 1 housed on a mobile platform.
 3. The system ofclaim 2 in which the mobile platform is free of fluid cooling devicesbetween the input point and the pressure vessel.
 4. The system of claim2 in which the mobile platform comprises a skid or trailer.
 5. Thesystem of claim 1 further comprising a gas blanket pressure sourceconnected to the pressure vessel.
 6. The system of claim 1 furthercomprising a housing containing the motive pump, the pressure vessel,the oil phase outlet, and the water phase outlet.
 7. The system of claim1 further comprising one or more pressure vessels connected by linescontaining pumps.
 8. The system of claim 1 further comprising a sampleremoval system connected to one or more of (A) the input point, (B) theline connecting the motive pump to the pressure vessel through the phaseseparator, (C) the pressure vessel, and (D) the water phase outlet. 9.The system of claim 8 further comprising one or more pressure vesselsconnected by lines containing pumps and in which the sample removalsystem is connected to one or more of the pressure vessels and the linesconnecting the pressure vessels.
 10. The system of claim 8 in which thesample removal system further comprises a filter.
 11. The system ofclaim 8 in which the sample removal system further comprises a fumehood.
 12. The system of claim 11 further comprising an air supply lineconnected to the fume hood.
 13. The system of claim 8 in which thesample removal system further comprises a cooling device.
 14. The systemof claim 13 in which the cooling device is a heat exchanger.
 15. Thesystem of claim 14 in which the heat exchanger circulates coolant from arefrigeration circulation system.
 16. The system of claim 15 in whichthe coolant is glycol.
 17. The system of claim 15 in which therefrigeration circulation system comprises a coolant supply line, acompressor, a return line, a coolant expansion tank and a pump.